It is now well-known that the comfort of a shoe is linked not only to correct anatomical configuration of the fit but also to correct outward permeation of the water vapor that has formed inside the shoe due to sweating.
Traditionally, vapor-permeable shoes are those which use natural materials such as leather or equivalent products, which however, in the presence of rain or bad weather, because of their vapor-permeable properties, do not ensure good waterproofing and indeed absorb rather easily water which can penetrate also through the stitched seams used for assembly.
For this reason, several types of shoes have been widely commercially available for a few years now which have an upper which is coupled to a lining with a vapor-permeable and waterproof membrane (for example made of a material such as Gore-Tex® or the like).
A shoe of this type is disclosed for example in U.S. Pat. No. RE34,890.
The shoe disclosed in such patent has a sock-shaped lining, constituted by a fabric which is coupled to a waterproof and vapor-permeable membrane, which not only prevents the water from penetrating into the shoe but also allows the foot to have outward vapor permeation.
This shoe, however, suffers drawbacks, since it still allows water to penetrate through the upper and to generate a retention of water between the waterproofing lining and the inner surface of the upper.
This causes the shoe to require considerable time to dry even after it has been used.
This stagnation phenomenon, moreover, causes an unpleasant feeling of moisture and coldness and a consequent increase in the weight of the shoe, therefore reducing user comfort.
Moreover, such shoe necessarily requires the use of an inner lining onto which a waterproof and vapor-permeable membrane is coupled, with a consequent increase in production costs.
The association between a membrane and a support, be it felt, fabric or leather, is widely known in the field of shoes and clothing, but adhesive bonding generally occurs always between simple materials, in rolls or pieces, substantially without stitched seams and overlaps. Examples of these methods can be found in patents DE2737756 and WO90/969.
The materials thus waterproofed, in order to be usable in the manufacture of a shoe, must be subsequently cut and sewn and the stitched seams in turn must be rendered waterproof, for example by means of suitable taping processes. However, this method has the disadvantage that such stitched seams are generally difficult to waterproof due to the different thicknesses of the different materials that compose the finished product.
Moreover, the stitched seams and the overlaps of the different elements that compose an upper for shoes are the most critical point in its manufacture.
In order to obviate this work method for manufacturing the shoe, a method has been devised in the past which might allow easy direct adhesion between the upper and the membrane. WO02/11571 and WO2004/112525 in fact disclose a process and equipment for waterproofing an upper which has already been manufactured.
Such process provides for turning inside out the upper of the shoe, at the last stage of its preparation, before it is associated with the sole, and fitting it on an appropriately provided last, which is rigid but can be adapted so as to tension the upper. Depending on the patent, one or two sheets of waterproof and vapor-permeable membrane provided with adhesive and heat-sealed at their ends are then pressed, by using particular equipment, such as for example a heated air bell press, against this three-dimensional assembly, which is constituted by the adaptable rigid last provided with the upper. Finally, the upper is removed from the adaptable last and is turned inside out so that it can be glued to the sole, after being associated with the assembly insole.
However, the above manufacturing method has some limitations and drawbacks.
A first limitation is related to the need for particularly elastic membranes, thus excluding all inextensible ones, on penalty of breakage during adaptation to the three-dimensional last.
A second limitation is related to the watertightness of the shoe, both proximate to sewn elements and inserts of the upper and in particular at the region where the sole is joined to the membrane-upper assembly. This method is unable to ensure perfect adhesion of the membrane proximate to the stitched seams and to the overlaps of the inserts which constitute the upper.
A third limitation is related to the manufacturing method, which is onerous in terms of production times and equipment, which is complicated due to the need to press a three-dimensional assembly.